The present invention relates to apparatuses and processes adapted to weld together the ends of a pair of conductors, wherein each conductor belongs to a coil member having a fork-like shape. Said members are inserted in slots of a core of an electric dynamo machine, and are normally referred to as “hairpins” in the art.
The hairpin has two straight legs connected together by a bridge-like transversal part. As a whole, the hairpin somewhat looks like an upside-down “U”, with the bridge having a cusp-like shape. Each leg has a free end for inserting the hairpin into the slots of a core, such as a stator or an armature.
The insertion is done by routing the free ends through the longitudinal entrances of the slots and by sliding them past the opposite side of the core, until the legs protrude outwards to a certain extent. Therefore, the hairpin bridges stay out on one side of the core, while the free ends stay out on the opposite side.
After having been inserted, the free ends are bent to be positioned in predetermined positions, where connections to other free ends are made by welding.
The present invention relates to apparatuses and processes for aligning the free ends along predetermined directions, so as to ensure that the free ends stay in predetermined positions prior to welding operations.
The welding operation can be carried out by resistance heating or through a laser beam that hits the heads of two free ends placed in adjacent positions in order to be connected. The material of both heads is thus melted and forms a connection joint having specified mechanic and electric characteristics, which closes the winding circuit of the core in accordance with a predetermined electric scheme.
A welding apparatus wherein the free ends are welded together by using an electric current for melting the material thereof is disclosed in European patent publication no. 1,043,828.
For the latest core applications, e.g. stators of electric motors or generators, the apparatuses and processes for free-end alignment have been refined in order to ensure greater accuracy in the positioning of the free ends prior to welding.
In addition, the devices involved in the alignment process must take less room and must apply a greater straightening force onto the conductors to align them, without damaging the conductors' insulation.
The increased hourly production of these core components has led to a reduction in the time available for performing the welding operation, so that there is less time for carrying out the alignment of the free ends.